Completely. The IRA proved at the peak of their notoriety that all they needed to do was make a threat of action. They closed Gatwick down for a day in '97 with only a phone call and forced Britain's Grand National horse race to be postponed with another, causing huge disruption, panic and anger. They got the attention they wanted but no-one lost a life. It surprises me that we don't see the tactic copied more often today.

Think about the Great War, that is World War One. It was for a while a war of attrition with Britain and France trying to bleed Germany white. It was truly terrible in a way that modern terrorism can never hope to be. So terrorists try to terrify even though they fall far short of being truly terrible. They are attempting a mindfuck, one that is mostly smoke and mirrors, with only 0.01% of the blood and gore of WWI.

The bathos of becoming unfunny practical jokers would destroy a terrorist movement. The terrorist must conduct himself so that, in the eyes of his victims, he is a fierce warrior who, when captured, has claims to the status of prisoner of war or political prisoner. If his victims are not frightened but are very annoyed then they will turn on him, sedate him heavily and lock him in the ward for the mentally retarded who are violent.

Bruce Schneier finds fault with the authorities saying that they defend us against 'movie plot' threats. I don't accept this criticism. Terrorist are constrained to operate within a socially constructed mythos that is mostly owned by their victims. Terrorists have to conduct attacks that have Hollywood's stamp of approval as 'terrorism'. Hollywood has no latitude on where it places its stamp of approval; it goes on visceral, primal dread, not left luggage.

Plus, they are unlikely to be caught for it. What are you going to do, prosecute people for forgetting a bag?